Updated through August 2026.
K’NEX has used several construction systems, including Classic K’NEX, Micro K’NEX and K’NEX Bricks. Most parts belong primarily to one of these systems, but K’NEX also developed parts that allow different systems to be combined.
These parts do not all work in the same way. Some are dedicated transition parts, some are adapters, and others are ordinary functional parts that were designed to work with more than one K’NEX system.
On this page, dual-system part is used for a component that can interact directly with two K’NEX construction systems. It does not mean that Dual-System is a separate K’NEX product family.
Three types of connection
Transition parts are specifically intended to connect different K’NEX rod and connector systems.
Adapters provide a connection between otherwise incompatible construction types, particularly between K’NEX rods/connectors and K’NEX Bricks.
Dual-system parts have another primary function — such as a hub, gear or motor — but contain connections that make them usable with more than one K’NEX system.
Classic ↔ Micro Transition Rods
Micro K’NEX uses substantially thinner rods than Classic K’NEX. Transition rods allow connectors from the two systems to be incorporated into the same structure.
Two lengths are known:
| Part no. | Length | Colour / variant |
|---|---|---|
| 530801 | 21 mm | Red / dark red / fluorescent red |
| 530802 | 21 mm | Grey |
| 530901 | 37 mm | Light blue / purple |
| 530902 | 37 mm | Fluorescent green |
| 530903 | 37 mm | Grey |
The 21-mm and 37-mm versions should therefore not be treated simply as colour variants of one transition rod.
Original parts documentation independently identifies 530801 as the 21-mm transition rod and 530902/530903 as 37-mm transition rods.
Classic ↔ Micro Reducer Clips
Another method uses a Classic-to-Micro reducer clip.
| Part no. | Colour |
|---|---|
| 531100 | Yellow / fluorescent |
| 531107 / 531107G | Black / grey variants |
Unlike the transition rods, the reducer clip provides a compact connection between rods of the two different systems.
531100 is documented in sets containing both ordinary Classic and Micro parts and is specifically identified as a Classic-to-micro reducer clip.
Classic + Micro Dual-System Hubs
Some small K’NEX hubs are especially interesting because the same hub can interact with both Classic and Micro rods.
Known 18-mm examples include:
| Part no. | Colour |
|---|---|
| 531200 | Black |
| 531203 | White |
| 531204 / 531607 | Grey / silver-grey |
| 531205 | Yellow |
| 99106L | Light grey |
These hubs are not adapters in the usual sense.
Their primary function is as wheel hubs. However, their connection geometry permits use with both rod systems. A Classic rod can therefore be fitted in one appropriate connection and a Micro rod in the other, allowing the hub to function as a physical transition between the systems.
The tyres fitted around these hubs are not themselves transition parts. Their compatibility results from the hub on which they are mounted.
Mechanical Transition — Classic ↔ Micro Gears
K’NEX also provided a way to transfer rotary motion between Classic and Micro K’NEX.
The relevant pair consists of:
| Part no. | Gear | Axle system |
|---|---|---|
| 509851 | Grey gear — approx. 34 mm, 34 teeth | Classic K’NEX |
| 513130 | Metallic-blue gear — approx. 15 mm, 14 teeth | Micro K’NEX |
509851 has a 6-mm (¼-inch) opening for a Classic K’NEX rod. 513130 has a 3-mm opening for a Micro rod. Their teeth are designed to mesh with each other.
This allows rotation from a Classic K’NEX axle — including a motor-driven axle — to be transferred to a Micro K’NEX axle.
The gears remain primarily Gear parts; their inclusion here describes their additional transition function.
Micro 8-way connector with a 6 mm (¼″) centre hole that accepts a Classic K’NEX rod. Also listed under Micro K’NEX Connectors.
| Part number | Part | Colour | Systems | Function / notes |
|---|
| 517200 | MICRO K’NEX Connector 8-way with 6 mm hole | Metallic Blue | Micro + Classic | Micro 8-way connector with a 6 mm (¼″) centre hole that accepts a Classic K’NEX rod. |
| 517201 | MICRO K’NEX Connector 8-way with 6 mm hole | White | Micro + Classic | Micro 8-way connector with a 6 mm (¼″) centre hole that accepts a Classic K’NEX rod. |
3310024 — 3-way Connector with 6 mm hole — Metallic Blue — Micro Connectors + Dual-System Parts
Micro K’NEX ↔ K’NEX Bricks
K’NEX also produced specialised components for combining the Micro system with K’NEX Bricks.
| Part no. | Description |
|---|---|
| 841700 | Orange Connector-Brick / transition pin adaptor |
| 843300 | Orange 2-leg Brick Adapter for Micro K’NEX |
| 843300L | Yellow 2-leg Brick Adapter — Classic K’NEX ↔ K’NEX Bricks |
These parts provide two different approaches to joining the much smaller Micro construction system to Brick-based structures.
841700 occurs alongside Micro components in mixed-system K’NEX sets and is documented as an orange transition rod/pin in Brick applications.
Classic K’NEX ↔ K’NEX Bricks
Classic K’NEX has corresponding Brick transition components.
| Part no. | Description |
|---|---|
| 841800 | Classic K’NEX ↔ Brick transition adaptor |
| 843300L | Yellow 2-leg K’NEX Brick Adapter |
841800 is documented as a transition rod for Bricks and appears in sets alongside 841700, demonstrating that K’NEX provided different transition components for the different construction scales.
Brick-to-Connector-Side Adapters
A further connection method attaches Brick construction to the side of a K’NEX connector.
| Part no. | Colour |
|---|---|
| 841900 | Grey |
| 841901 | Blue |
These are identified as Brick-to-connector-side adaptors and should not be confused with the rod-like transition parts above.
Dual-System Motors
Some K’NEX Brick motors also cross system boundaries.
They remain Motors, not adapters, but their construction combines Brick-compatible bodies with Classic K’NEX rod, axle or wheel connections.
Known examples include:
99132 — Brick Spring Motor
A Brick-based spring motor that interacts with the Classic K’NEX rod system.
99133 — Brick Battery Motor
A battery-powered Brick motor with Classic-size axle/wheel connections.
99133R — Brick Battery Motor, red-axle variant
99205 family — Motorized Car Base
Brick-compatible motorized bases with Classic K’NEX wheel/axle connections.
These parts illustrate why dual-system is useful as a functional description: an item can remain primarily a Motor while simultaneously providing a connection between two K’NEX construction systems.
Special Transition Parts
Some licensed ranges contain specialised transition components that do not yet have a verified standard K’NEX part number.
One example occurs in the K’NEX Titanfall range: a small black wheel-like component can be used as a Micro/Classic transition.
Its catalogue identifier is currently:
K69508/11
This is not presented as an official K’NEX part number. Until an original K’NEX number can be verified, the component should remain listed separately from the regular dual-system hub family.
Classification
Parts on this page retain their normal primary classification.
A dual-system hub remains a Hub.509851 and 513130 remain Gears.
Brick motors remain Motors.
Brick adapters remain Adapters.
This page therefore provides an additional functional view of the catalogue rather than creating a new parts family.
It also explains an important feature of the wider K’NEX system: Classic, Micro and Bricks were not always isolated construction systems. K’NEX deliberately provided several different ways to combine them in a single model.
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